This invention relates to a transmit beamformer for a medical diagnostic ultrasound system. In particular, an architecture and method for implementing delays as a function of channel within an ultrasonic transmit beamformer are provided.
Transmit beamformers generate electrical waveforms in a plurality of channels for associated transducer elements of a transducer array. By applying different delays to different channels, a beam of ultrasound energy is steered and focused.
Transmit beamformers generate the transmit waveforms and apply delays for each channel separately. For example, U.S. Pat. No. 5,675,554 discloses applying a delay for each channel, such as shown in FIG. 3 of the ""554 patent. An absolute delay for each channel is implemented by delaying a start of waveform generation or delaying the generated waveform. Transmit beamformers may use random access memories or first-in first-out buffers for each channel to delay the transmit waveform. A start-of-transmit signal is provided to each channel. In response to the absolute delays, the transmit waveform of each channel is delayed the same or differently than adjacent channels or other channels. Digital counters may be used to delay the start-of-transmit signal.
The present invention is defined by the following claims and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiments described below include a method and system for applying absolute delays between groups of channels and applying relative delays to channels within the groups of channels. For example, every fourth channel is responsive to an absolute delay from a controller. The delay for channels between every fourth channel are set as relative delays corresponding to a further delay in addition to the absolute delay.
In a first aspect, a method for ultrasound transmit beamforming is provided. Absolute delays are applied to at least two of a plurality of groups of channels and relative delays are applied to channels within each of the groups of channels.
In a second aspect, an ultrasound transmit beamformer system for focusing transmit beams is provided. A first plurality of channels comprise respective transmit pulse memories. A second plurality of channels without transmit memories but with delays are provided.
In a third aspect, an ultrasound transmit beamformer for focusing ultrasonic beams is provided. A plurality of programmable sequence generators for a first respective plurality of channels is provided. The programmable sequence generators operate as function of absolute delays. A plurality of relative delays are provided for a respective second plurality of channels. The channels of the second plurality of channels are different than the channels of the first plurality of channels.
Further aspects and advantages of the invention are discussed below in conjunction with the preferred embodiments.